The role of monocytes and macrophages in inflammatory and immune responses has yet to be characterized at the molecular level. Although it is clear that activated macrophages an monocytes release a large number of biological mediators at the site of inflammation, the effect of these mediators upon lymphocytes, fibroblasts, endothelial and possibly other cells remains to be determined. A single pluripotent monokine, Interleukin 1 (IL 1), has been demonstrated to affect the inflammatory process at several stages. Although Interleukin 1 has been extensively investigated, it has not been purified to homogeneity in a biologically active form. In addition, monoclonal antibodies to IL 1, which are required to measure IL 1 in biological fluids, to affinity purify IL 1, and to isolate polysomal mRNA for gene cloning, have yet to be developed. Once the primary sequence of IL 1 has been determined, it will be possible to predict antigenic regions to select possible sequences for nuceotide probes specific for IL 1 coding m RNA, and to indicate possible amino acid sequences for antagonists of IL 1 which may be potential anti-inflammatory and anti arthritic agents. It is proposed to determine the primary structure of human IL 1 purified to homogeneity by SDS-polyacrylamide gel electrophoresis. (2) To prepare homogeneously purified human IL 1 which retains biological activity. (3) To prepare monoclonal antibodies and heteranisera to human IL 1. (4) To use the abovementioned antibodies to develop ELISA assays which can quantitate IL 1 levels in complex bodily fluids, and to prepare affinity reagents which can remove IL 1 from these fluids. (5) To continue biological studies using homogeneously purified, biologically active IL 1 to unequivocally establish that a single molecule elevates fever, induces fibroblast proliferation stimulates collagenase release from fibroblasts, stimulates acute phase reactants when injected in vivo, induces B and T lymphocyte proliferation and granulopoeisis, and possibly affects vascular permeability.